A hot start on an Airbus A320 (or any jet engine) occurs when the engine's exhaust gas temperature (EGT) exceeds acceptable limits during the start sequence. This situation typically happens when there is insufficient airflow through the engine to cool it during the combustion process. If not managed, a hot start can cause serious damage to the engine.

Causes of a Hot Start

1. Insufficient Airflow
   
   

   • Low bleed air pressure from the APU or external source during start.

   • Obstructed airflow due to damaged or malfunctioning components.

2. Fuel Issues
   
   

   • Excessive fuel flow during ignition.

   • Premature fuel introduction before the engine reaches the correct rotation speed (N2).

3. High Ambient Temperatures
   
   

   • Operating in hot weather conditions can increase the likelihood of a hot start.

4. Mechanical Problems
   
   

   • Faulty igniters or engine components.

   • Compressor or turbine damage restricting airflow.

Detection

During the engine start, the following are monitored:

1. Exhaust Gas Temperature (EGT)
   
   

   • A rapidly rising EGT approaching or exceeding the limit indicates a hot start.

2. N2 Speed (High-Pressure Compressor)
   
   

   • If N2 remains low despite fuel being introduced, the airflow may not be sufficient, leading to a hot start.

3. Abnormal Engine Sounds or Vibrations
   
   

   • May indicate combustion instability.

Procedure for Handling a Hot Start

If a hot start is detected during the start sequence:

1. Abort the Start
   
   

   • The start is immediately aborted by switching the ENG MASTER switch to OFF.

   • The engine’s starter is typically kept engaged for a few seconds to cool the engine by motoring airflow.

2. Dry Cranking
   
   

   • After the start is aborted, a dry cranking cycle may be performed to clear excess fuel and cool the engine.

3. Inspection
   
   

   • Maintenance personnel may need to inspect the engine for damage before another start attempt.

Prevention

• Ensure adequate bleed air pressure from the APU or ground air source.

• Follow standard operating procedures for engine start, including proper fuel introduction timing.

• Regular maintenance to ensure all engine components are functioning correctly.

Hot starts are taken seriously, as repeated or prolonged occurrences can lead to significant engine damage.